Webhooks should support media uploads

Matterbridge is a software project that facilitates the seamless integration of chatrooms that exist on disparate chat protocols. It supports Discord chats by interfacing with the bot and webhook APIs, and can use either of those APIs to post messages that are sent in chats using other protocols.

However, the Discord webhook API, according to the project (see https://github.com/42wim/matterbridge/wiki/FAQ#filesimages-not-getting-uploaded- ), lacks the functionality necessary to upload media. Matterbridge /is/ able to upload media by using the Discord bot API to post messages, but this option comes at the cost of the webhook API's ability to spoof the usernames and avatars of users on other platforms.

Extending the webhook API to allow for uploading media (as a user or a bot could)would allow for projects such as Matterbridge to be able to simultaneously support media upload and username/avatar spoofing in the same messages.